openssl_get_publickey() 的运行结果在php7和php5.6上不一样？？？？

hi everyone,

today i meet a strange problem while the function openssl_get_publickey() runs well in php 7 while report an error in php5. 6.16 and php5.5.12

here is the test code:

//define a pem formatted string varaible named $key
$key = <<-----BEGIN PUBLIC KEY-----
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCnxj/9qwVfgoUh/y2W89L6BkRAFljhNhgPdyPuBV64bfQNN1PjbCzkIM6qRdKBoLPXmKKMiFYnkd6rAoprih3/PrQEB/VsW8OoM8fxn67UDYuyBTqA23MML9q1+ilIZwBC2AQ2UBVOrFXfFl75p6/B5KsiNG9zpgmLCUYuLkxpLQIDAQAB
-----END PUBLIC KEY-----
EOF;

//get the public key
$res = openssl_get_publickey($key);
var_dump($res);

?>

while in php7.0.0 the result is normal and correct here is the output
{

D:\wamp64\www\php\index.php(50) : eval()'d code:24:resource(4, OpenSSL key)

}

but not the same result in php 5.6.16 and php 5.5.12 here is the output
{

D:\wamp64\www\php\index.php(50) : eval()'d code:24:boolean false

}

so can you help me with the problem???